AUTISM AND OTHER PERVASIVE DEVELOPMENTAL DISORDERS - EXPLORING THE DIMENSIONAL VIEW

Objective: To examine empirical data on children with autistic disorde r (AD), Asperger's disorder, and pervasive developmental disorder not otherwise specified (PDD-NOS) for continuities or distinguishing featu res between disorders and to see to what extent the Diagnostic and Sta tistical Manual of Mental Disorders (DSM-IV) diagnostic criteria refle ct observed data. Method: Studies were identified in 4 ways. 1) A Medl ine search from 1976 to the present of articles with the key words aut ism, pervasive developmental disorder, autistic spectrum disorder, and Asperger, of these articles, those with mesh headings or textwords '' cluster,'' which identified cluster analyses deriving pervasive develo pmental disorder (PDD) subtypes, were retained. 2) The Journal of Auti stic and Developmental Disorders from 1990 to the present was hand-sea rched to identify other empirically derived studies on diagnosis, prev alence, classification and validity of PDD subtypes. 3) Key review art icles were searched for their references. 4) The references of all ide ntified articles were searched. Results: Eight cluster studies were re tained for their relevance to diagnostic issues, as were 7 empirically derived studies delineating clinical characteristics of children with AD, Asperger's syndrome, or PDD-NOS. Data suggest that children with PDD may fit into 1 of 2 overlapping groups, including a lower-function ing group with greater developmental compromise, social aloofness, and a greater number of autistic symptoms and a higher-functioning group with higher IQ, fewer autistic symptoms, and more prosocial behaviour. The PDD subtypes resemble each other and can be seen as existing on a continuum, differing only by degree of impairment. Conclusion: Childr en exhibiting the triad of autistic impairments can be seen as sufferi ng from disorders on a PDD continuum. While the DSM-IV does identify a lower-functioning autistic group (AD), the higher-functioning group i s less well sewed. Asperger's disorder as defined in the DSM-IV is not clearly distinguishable from AD and PDD-NOS, and the PDD-NOS subcateg ory is not operationalized. Further research is required to elaborate criteria for the higher-functioning PDD group, and measures related to etiology, outcome, and treatment response may help determine which di agnostic criteria can meaningfully separate one disorder from another.